Darren MichaelsFrom left, John Cho, Neil Patrick Harris and Kal Penn star in what is likely to be this yearâs weirdest holiday-themed movie, âA Very Harold & Kumar 3D Christmas.â

Ah, the wonders of new technology.

At one point, the makers of “A Very Harold & Kumar 3D Christmas” use it to hurl a handful of excrement straight at the camera. Throughout the film, it’s utilized to blow pot smoke right in our faces.

The first is a good metaphor for what the film’s crude story does, again and again.

The second is perhaps a prescription for the only way someone might sit through it and laugh.

The Cheech and Chong for a new generation, “Harold & Kumar” debuted in 2004, telling the story of two very stoned New Jerseyans in search of a sackful of White Castle belly bombers.

A 2008 sequel then sent them to Guantanamo Bay, and later stranded them among some particularly backward backwoods people.

In their latest addled adventure, the two have grown apart. Harold is living in the suburbs and trying to start a family; Kumar is still stuck in their old Hoboken apartment, trying to light his bong.

But circumstances — including the search for a Christmas tree, a flight from an angry mobster, and the inevitably strange encounter with Neil Patrick Harris — are bound to draw them together. And make stone-cold — or just stoned — H&K fans giggle.

The rest of us, though, are likely only to sit there and shake our heads in wonder. Or mild disgust.

“Harold & Kumar” used to have a what-the-hell, multi-culti attitude, mostly because of its easygoing leads, John Cho and Kal Penn. But this film feels a little meaner and indulges in too many lazy racist jokes (gangbanging Hispanics, Asians who all look alike) with the usual excuse of “Hey, we’re just being ironic.”

Nor do a lot of the drug jokes play. Yes, dude, we get that Kumar loves the herb; we’re cool with that. But there’s a whole subplot about a baby who gets accidentally dosed with pot, then cocaine, and finally Ecstasy. The toddler is so toasted! Man, it’s like hilarious, right?

Except, um, no, it’s not. It’s really, really not.

At least Neil Patrick Harris is a stitch, once again playing a funhouse version of himself. This time, the gag is that his real-life coming-out party was all an elaborate ruse; he only pretends he’s gay so he can hit on ingénues with impunity. (Clay Aiken does the same thing, he confides.)

It’s a good joke, easily the best one in the movie. There’s also some interesting use of 3-D and one brief, nicely demented sequence in which a hallucinating Harold and Kumar imagine that they’ve become animated clay figures (even if the chance to really burlesque old Christmas TV shows isn’t seized).

But the rest of the movie is just, well, pot smoke blown in our faces and excrement thrown at the screen — figuratively and literally.